This application is related to and claims priority from Japanese Patent Applications No. 2001-106406 filed on Apr. 4, 2001 and No. 2001-359585 filed on Nov. 26, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a hybrid water heater in which a combustor for heating water is combined with an electrical heating unit having a hot water tank.
2. Description of Related Art
As a conventional water heater, an electrical water heater or a combined water heater is used. In the electrical water heater, water is heated by an electrical heating member, and the heated water (hot water) is stored in a hot water tank while its temperature is maintained. However, in the electrical water heater, when a large amount of hot water is used at one time, the amount of hot water in the hot water tank may be deficient. Accordingly, it is necessary to enlarge the hot water tank, for preventing the hot water in the hot water tank from being deficient.
On the other hand, in the combined water heater, because a combustion heating unit using a combustor is simply combined with the electrical water heater, an entire system structure of the combined water heater becomes complex. Accordingly, a control valve, for switching one flow of hot water from the electrical water heater and hot water from the combustion heating unit, is required, for example.
In view of the foregoing problems, it is an object of the present invention to provide a hybrid water heater which has a simple combination structure while it can effectively prevent hot water from being deficient.
According to the present invention, in a hybrid water, an electrical heating unit and a combustion heating unit are disposed to heat water to be stored in a hot water tank. The combustion heating unit includes a combustor for heating water in a chamber. The chamber has a first water port at an upper side, through which heated water flows from the camber into an upper side in the hot water tank, and a second water port at a lower side, through which water at a lower side in the hot water tank flows into the camber. In the hybrid water heater, the hot water tank and the chamber are disposed to communicate with each other through the first water port and the second water port, in such a manner that the water heated in the chamber is stored in the hot water tank at the upper side using natural convection due to a temperature increase of the water in the chamber. Accordingly, even in such a condition where hot water deficiency occurs when only using the electrical heating unit, hot water heated by the combustor in the camber can be stored in the hot water tank at the upper side. Therefore, the hot water deficiency can be effectively prevented without particularly enlarging the size of the hot water tank. Further, the high-temperature hot water due to the gas combustion flows into the hot water tank at the upper side using the natural convection. Therefore, a control valve and the like, for switching a hot water circuit between the electrical heating unit and the combustion heating unit, is not required, thereby simplifying an entire system structure of the hybrid water heater. Furthermore, in the hot water tank, the high-temperature hot water is not mixed with low-temperature water at the lower side, and is stored at the upper side. Therefore, the high-temperature hot water due to the gas combustion can be effectively used for a supply.
Preferably, a control unit for controlling the combustion operation of the combustor has determining means for determining whether or not hot water in the hot water tank is deficient for a supply. When it is determined that the hot water in the hot water tank is deficient, the combustor is operated by the control unit to heat water in the chamber. Alternatively, when it is determined that a hot water state in the hot water tank is a state incapable to supply hot water to a hot-water supply equipment, the combustor is operated by the control unit to heat water in the chamber. Alternatively, when a command, for supplying hot water higher than that of the hot water in the hot water tank, is input from a user, the combustor is operated by the control unit to heat water in the chamber. Accordingly, even when the size of the hot water tank is made smaller, necessary hot water can be rapidly supplied from the hot water tank.